a crude method of limiting long-prefix propagation

[Joel M. Halpern]

If we are going to look down this path, for some cases at least, 
DIST_LIST_EXCL (which lists where NOT to send the information) would also 
seem useful.
Yours,
Joel M. Halpern

At 06:37 PM 3/24/01 -0800, Yakov Rekhter wrote:
>Ben,
>
> > Yakov,
> >       Can you provide a reference for this?  I am rather far along in
> > my definition of the PROP_PATH and its behavior, but any input like this
> > is welcome.
>
>see below...
>
>Yakov.
>---------------------------------------------------------------------
>    7.12.5  DIST_LIST_INCL
>
>       DIST_LIST_INCL is an optional transitive attribute.  It
>       shall be recognized upon receipt by all routers.  When present,
>       this attribute lists the ASs of the routing domains to which
>       the routing information may be distributed.
>
>       When a router receives an UPDATE message that contains the
>       DIST_LIST_INCL attribute, then the receiving router shall
>       not redistribute the associated routing information to any
>       router which is not a member of at least one autonomous system
>       whose AS is contained in this attribute.
>
>       A router shall redistribute only that information which has
>       been locally selected as a route, and shall redistribute it
>       only to autonomous systems which are both adjacent to it and
>       are included in the distribution list.  A router may distribute
>       the information to any adjacent router that is a member of
>       any routing domain or confederation whose AS is contained in
>       DIST_LIST_INCL.  A router is not required to distribute the
>       routing information to every autonomous system whose AS is
>       listed.
>
>       If a router receives an UPDATE message that doesn't contain
>       the DIST_LIST_INCL attribute, then it may distribute the
>       routing information to all adjacent routers.  Alternatively,
>       the local router may also add a DIST_LIST_INCL attribute, to
>       the route information.  If the DIST_LIST_INCL attribute is
>       present and has a length of zero octets, then the routing
>       information may be used locally, but shall not be advertised
>       to any other router.
>
>       When it originates an UPDATE message which describes a route
>       to destinations located in its own routing domain, a router
>       may append the DIST_LIST_INCL attribute, in accordance with
>       its local policies.
>
>       If a router chooses to advertise a route which was learned
>       from an UPDATE message which already contained the DIST_LIST_INCL
>       attribute, the advertising router may modify this attribute
>       by pruning the set of ASs included in the list.  If a router
>       chooses to prune the set, it shall not delete the AS of its
>       own autonomous system.  However, if the reduced list is empty
>       (that is, has a length of zero), then the router shall not
>       advertise the routing information to any router located in
>       a different routing domain.